Switching arrangement in telephone plants



April 19, 1932. -V|GREN 1,855,074

SWITCHING ARRANGEMENT IN TELEPHONE PLANTS Filed March 15, 1931 Patented Apr. 19, 1932 UNITED STATES PATENT OFFICE s'rnn DANIEL VIGREN, or s'r'ocxnonm, SWEDEN, ASSIGNOR T TELEFONAKTIEBO:

. LAGET L. M. ERICSSON, or STOCKHOLM, SWEDEN, A COMPANY or SWEDEN swrrcnme ARRANGEMENT 11v TELEPHONE PLANTS Application filed March 13, 1931, Serial No. 522,403, and in Sweden March 21, 1930.

The present invention relates to the switching oftalking connection in telephone plants in which one or all of the speaking devices during a certain period of time are adapted to be made inoperative. This is the case for example in so called paystations or coin collector telephone stations to which the present invention is particularly applicable.

The pay stations hitherto used are generally so disposed thatthe calling person upon his callingup the exchange enters into communication with an operator who in turn calls up the wanted subscriber,waits for his reply, controls that the-correct subscriber has been called, requests the calling person to pay the fee, and finally controls the payment. Thereupon the calling person is connected to the called subscriber. This known arrangement has, however, the inconvenience that the time of the operator-is engaged too much which in turn necessarily makes the charges comparatively elevated for a call from apay station. To reduce the work of the operator it has been proposed to equip the pay station with mechanical devices of such a nature that the calling person only by inserting his coin is enabled to call up the telephone exchange, the coin simultaneously short-circuiting the microphone by means of a contact. When the operator replies an electromagnet in the pay station is energized whereby the short circuit of the microphone is removed'so long as she is connected into the line. After calling the wanted subscriber the microphone of the calling person is again short-circuited untilby pushing a button he drops the coin into the box, the short circuit of the microphone being then removed. Said proposed arrangement has, however, the inconvenience that sensitive mechanical devices and relays upon which the reliability of the switching operation depends must be disposed in the pay station. The present invention has for its'object to r enable the calling person to hear the called subscriber but not to speak with him before he has brought about a shifting'of the circuits by actuating a debiting or paying device disposed on the pay station whereby the talking connection is completed.

According to the invention a numberof rectifiers are connected into circuit for this purpose.

The invention is applicable both to pay stations having COlIl'COllGCtOI' and to pay stations having call meters in which former case the calling person must drop the'prescribed amount into the coin box by actuating his paying device'whereas in the-latter case he must actuate the call meter before talking connection may be established. i

The invention will be more closely de scribed with reference to the accompanyingdrawings, Figures 1 and 2. The telephone apparatus is substantially connected up-in a manner known per se but provided with two rectifiers L and L In the one line branch there is included a high resistance R which normally is short circuited by the paying or debiting device D. In the telephone exchange A and B are the current feed relays of the apparatus, BR its cut ofirelayyfor calls, and SVR its current reversing relay.

The apparatus inFigure l operates in the following manner. When the microtelephone is lifted the following current path is formed. The plus pole of the battery, the relay A, the contact 1, the line'branch a, the contact D, the rectifier L in its direction of unobstructed'current' passage, the microphoneM, the induction coil I, the line branch 6, the contact 4, the relay B, and the minus pole. Parallelly across the rectifier L and the microphone M the rectifier L is con nected up in such a manner that it blocks current in the direction just mentioned. The relays A and B are energized. The call indicating lamp AL islighted over the contacts 5 and 6. 'When the operator replies by inserting the plug SS in the jack SJ the following current path is formed. The minus pole, the relay SR ofthe thirdwire 0 of the plug, the third wire 0 of the ack, the winding L of the relay SVR, the relayBR, and'the-plus pole. The relay: SVR is so adjusted that it does not attract its armature for this current whereasthe relay. BR attracts its armature and opens its contact 6,

the'lamp AL being then put oil", and closes the contact 3 whereby the relay receivesholdingcurrent' over the contact 5. The calling the minus pole.

person may now ask the operator for the wanted subscriber. Then the operator calls up said subscriber and the speaking switch EOR is actuated. The following current path is then formed. The plus pole, the resistance SRR, the third wire 0, the winding L ofxthe relay SVR, the contact 3, the contact 5, and the minus pole. The winding L of the relay SVR is so adjusted that the appertaining armature is attracted for this current and receives holding current over the followingv current path. The plus pole,the resistance P, the contact 8, the winding H Also the contacts 1 and 1 are opened whereas the contacts and 11 are closed which results in that the current direction through the pay station isreversed the following current path being then estab- .li'shed. The plus pole, the relay A, the contact ll, the linebranch b, the induction coil 1, the rectifier L in its direction of unobstructed passage, the contact D, the line branch (1,

the contact 10, the relay B, and the minus tion of unobstructed passage.

pole. The microphone M will then be devoid of. current because it is series connected with the rectifier L in its locking direction and is shunted by the rectifier L in its direc- When the called subscriber replies the calling person is .able to hear his voice but may not speak with him before he actuates his debiting or paying device D, the contact at D being then opened and theresistance R connected up in series with the line, i The current is then reduced for a moment so that the relay A is de-energized whereas the relay'B holds its armature. Then the following current path is established. The minus pole, the contacts 12, 13 pole.

and 8, the resistance P, andthe plus ThewindingH of the relay SVR is Q then short-circuited which results in that the relay SVR is deenergized. The contacts 10 and 11 are opened andthecontacts 1 and 4 closed so that the current through the pay station is reversed The microphone is d again passed by current and the calling person isenabled to speak with the called subscriber.

.Figure 2 shows diagrammatically another switching arrangement according to the in vention. Aconnection completed by an operator or automatic selectorsis shown just 7 before a called subscriber AA lifts his microtelephone. The current paths present then noidifferences from an ordinary talking connection. When the called subscriber lifts his microtelephone the following current path is formed. The plus pole, the one Winding of therelay BSS, theline branch at, the called I subscribers station, the line branch b, the c the other winding of the relay BSS, and the minus'pole. The relay BSS is energized the followingvcurrent path being then formed. The plus pole, the contact 5, the relay SVR,

of the relay SVR, the contact 9, and.

the contact 6, and the minus pole. The relay SVR is energized the contacts 1 and 2 opened and the contacts 3 and 4 closed which results in that the current through the pay station isreversed and the following current path established. The plus pole, the relay A, the contact 3, the line branch 6, the induction coil I, the rectifier L in its directionof unobstructed current passage, the contact D, the'line branch 0:, the contact 4, the relay B, and the minus pole. The microphone M will now be currentless for the same reason as is above stated in conjunction with Figure 1. The calling person is thus ablectohear the voice of the call-ed subscriber but maynot speak with him before he actuates his paying device, the contact D being then opene'd and the resistance R connected in series with the line. The current isithen reduced fora mo..- inent so that the relay A is deenergized whereas the relay B holds its armature. The following current path is then established. The plus pole,-the contact 7 the contact '8, the relay TR, and the minus pole. The relay TB is energizedand receives holding current over the contacts 10, 11 and 9'until both subscribers. have hooked up their inicrotelephones. Further therelayT opens its contact 6 which results in that the relay SVR is deenergized. The c0ntacts'3- and 4; are opened and'the contacts 1 and 2 closed so that the current through the pay station is .re-

versed. Then the microphone M will again be passed by current in similarity with the fiers has not been moreclosely-stated. Itv

is, however, readily understood that both copper rectifiers and other metal rectifiers as well as electron valve rectifiers maybe used. If metal rectifiers are used it is ad visable to connect one rectifier in series with the microphone and another rectifier across H the microphone and the former rectifier. On

the other hand, if rectifiers having a more ideal operation are used it is sufficient to use only one rectifier which then may be disposed either with series or in shuntwiththe microphone, due consideration being taken to the correctness of the direction'of'unobstructed current passage.

The invention is not restricted to the above described purposes but maybe applied in a plurality of other switching arrangements where it is desirable to'render circuits current carrying or currentless .by reversingthe current direction.

Iclaimzf- 7 1. A telephone 'pay'stationcomp-rising a microphone, a microphone current source, rectifying means for blocking microphone current of the one direction, means for connecting the current source to the microphone in the blocking direction prior to payment,

and means for connecting the current source to the microphone in the reversed direction upon payment.

2. A coin collector telephone station comprisinga microphone, a microphone current source, rectifying means for blocking microphone current of the one direction, means for connecting the current source to the microphone in the blocking direction prior to payment, and means for connecting the current source to the microphone in the reversed direction upon payment;

3. A telephone pay station comprising a microphone, a debiting device, a microphone current source, rectifying means for blocking microphone current of the one direction, means controlled by the debiting device for connection of the current source into blocking direction prior to actuation of the debiting device and automatically into reversed direction subsequent to actuation of the debiting device.

at. A coin collector telephone station comprising a microphone, a coin operated debiting device, a microphone current source, rectifying means for blocking microphone current in the one direction, means controlled by the debiting device for associating the current source with the microphone in blocking direction prior to payment and automatically into reversed direction upon actuation of the debiting device.

5. A telephone pay station comprising a microphone, a microphone current source, a rectifier series connected with the microphone, means for connecting the current source to the microphone in the blocking direction of the rectifier prior to payment, and means for connecting the current source to the microphone in the direction of unobstructed passage through the rectifier upon payment.

6. A telephone pay station comprising a microphone,'a microphone current source, a rectifier connected across 'the microphone,

means for connecting the current source to the microphone in the direction of unobstructed passage through the rectifier prior to payment and in the blocking direction of the rectifier upon payment.

7. A telephone pay station comprising a microtelephone, a microphone current source, a rectifier series connected with the microphone, another rectifier connected across the microphone and the series connected rectifier, the blocking direction of the series connected rectifier being reversed to that of the shunted rectifier, means for connecting the current source to the microphone in the blocking direction of the series connected rectifier prior to payment and automatically in the blocking direction of the shunted rectifier upon payment.

microphone current of the one direction, and a debiting device, in combination with a'telephone exchange comprising a microphone current source, and switching means for connecting the current source to the microphone in the blocking direction prior to actuation of the paying device and in the reverse direction upon actuation of'the debiting device.

9. A telephone pay station comprising a microphone, rectifying means for blocking microphone current of the one direction, and a debiting device, in combination with a telephone exchange comprising a microphone current source, and switching means for connecting the current source to the microphone in the blocking direction prior to actuation of the paying device and in the reverse direction upon actuation of the debiting device and finally two Wires connecting the pay station with the exchange.

In testimony whereof I aflix my signature.

STEN DANIEL VIGREN.

8. A telephone pay station comprising a microphone, rectifyingmeans for blocking 

